The invention relates to tools that assist with the selection and attachment of aortic heart valve prostheses. In particular, the invention relates to tools to help select a prosthesis with the correct size and markers for marking the aortic tissue to guide placement and attachment of the prosthesis.
Prostheses, i.e., prosthetic devices, are used to repair or replace damaged or diseased organs, tissues and other structures in humans and animals. Prostheses must be generally biocompatible since they are typically implanted for extended periods of time. For example, prostheses can include artificial hearts, artificial heart valves, ligament repair material, vessel repair, surgical patches constructed of mammalian tissue and the like.
Prostheses can be constructed from natural materials such as tissue, synthetic materials or a combination thereof. For example, prostheses formed from purely synthetic materials, such as mechanical heart valve prostheses, can be manufactured, for example, from biocompatible metals, ceramics, carbon materials, such as graphite, polymers, such as polyester, and combinations thereof. Mechanical heart valves can be manufactured with rigid occluders or leaflets that pivot to open and close the valve, or flexible leaflets that flex to open and close the valve.
Although mechanical heart valves with rigid pivoting occluders have the advantage of proven durability through decades of use, they are associated with blood clotting on or around the prosthetic valve. Blood clotting can lead to acute or subacute closure of the valve or associated blood vessel. For this reason, patients with implanted mechanical heart valves remain on anticoagulants for as long as the valve—remains implanted. Anticoagulants impart a 3-5% annual risk of significant bleeding and cannot be taken safely by certain individuals.
Heart valve prostheses can be constructed with flexible tissue leaflets or polymer leaflets. Prosthetic tissue heart valves can be derived from, for example, porcine heart valves or manufactured from other biological material such as bovine pericardium. Biological materials in prosthetic heart valves generally have profile and surface characteristics that provide laminar, nonturbulent blood flow. Therefore, intravascular clotting is less likely to occur than with mechanical heart valves.
However, prosthetic tissue heart valves are limited by a tendency to fail beginning about seven years following implantation. Calcification, i.e., the deposition of calcium salts, especially calcium phosphate (hydroxyapatite), appears to be a major cause of degeneration. Thus, tissue heart valves are generally used for older patients who experience less calcification and require the valve for shorter lengths of time. In addition, various approaches have been developed to reduce the effects of calcification, such that tissue heart valves will have greater durability. As these approaches achieve demonstrated long term effectiveness, tissue heart valves likely will find greater use.
In a heart, blood flow between the respective atria and ventricles and flow from the ventricles are controlled by heart valves. Blood flow from the right ventricle of the heart passes into the pulmonary artery. Blood flow from the left ventricle of the heart passes into the aorta. Blood flow between the left ventricle and aorta passes through the aortic heart valve—located near the connection of the aorta with the heart. The natural aortic heart valves has three leaflets that open to allow flow into the aorta and close to prevent back flow into the left ventricle.
Tissue leaflets have sufficient flexibility to open and close. Each of the three leaflets of a natural valve are attached to the cylindrical wall of the aorta along a nonplanar curve. Coronary arteries join the aorta near the valve. A commissure post can block or partially block a coronary artery. This complicates the placement of a stentless aortic prosthesis.
Attachment of a stentless aortic heart valve is complicated since suturing must be performed on both inflow and outflow edges of the valve to secure the valve. Significant pressures are exerted against the valve in use. Due to the pressures, it is desirable to suture the prosthetic valve along the commissure supports to ensure that the valve does not pull away from the aorta. That suturing along the commissure supports is difficult because the valve is within the aorta during the implantation.